Routing devices within a network, often referred to as routers, maintain tables of routing information that describe available routes through the network. Upon receiving an incoming packet, the router examines information within the packet and forwards the packet in accordance with the routing information. In order to maintain an accurate representation of the network, routers exchange routing information in accordance with a defined routing protocol, such as Interior Gateway Protocol (IGP) or Border Gateway Protocol (BGP).
Multi-protocol Label Switching (MPLS) is a suite of protocols used to engineer traffic patterns within Internet Protocol (IP) networks. By utilizing MPLS, an ingress or root node can request a path through a network to an egress or leaf node, i.e., a Label Switched Path (LSP). An LSP defines a distinct path through the network to carry MPLS packets from the ingress node to the egress node. A short label associated with a particular LSP is affixed to packets that travel through the network via the LSP. Routers along the path cooperatively perform MPLS operations to forward the MPLS packets along the established path. A variety of protocols exist for establishing LSPs, e.g., the Label Distribution Protocol (LDP) and the Resource Reservation Protocol with Traffic Engineering extensions (RSVP-TE). LSPs may be used for a variety of traffic engineering purposes including bandwidth management and quality of service (QoS).